Anesthesia devices are used in anesthesia in order to maintain the patient in a pain-free and unconscious state during a surgery. These anesthesia devices comprise essentially gas-mixing units, a respiration drive, as well as feed lines leading to the patient. Various gases, e.g., oxygen, air and nitrous oxide, are sent to the gas-mixing unit. Another dispensing element in an anesthesia device is an anesthetic evaporator, by which anesthetics are added into the gas, which is then sent to the patient via feed lines.
DE 199 07 362 A1 shows a device for mixing at least one first and one second gas component by means of a Venturi nozzle, with a propellant gas port for propellant gas, a suction duct and a gas outlet. To improve the ratio of the gas components to be mixed relative to one another, a first bypass line deflecting a first partial flow of the first gas component to the suction duct with a first throttling point is provided between the propellant gas port and the suction duct.
DE 695 15 391 T2 describes an anesthesia system with a fresh gas source, wherein a defined inflow of fresh breathing gas into a breathing circuit is controlled on the basis of a rate of flow detected by a flow meter. The anesthesia system is designed such that the flow meter can be calibrated, while the system is being operated, so that a supply of fresh breathing gas into the breathing circuit is made possible continuously or essentially continuously.
U.S. Pat. No. 7,438,072 B2 describes a portable anesthesia device with a mixing system for mixing gases, with an anesthetic evaporator, with an inlet and outlet for carrier gases, wherein the gas flow and the mixing of gases are controlled by means of a control and control means such that an essentially constant anesthetic gas concentration is obtained in the gas flow to the patient.
CN 201308700 Y shows a portable anesthesia device with a pressure-reducing valve, wherein the pressure-reducing valve is connected to a pressurized oxygen cylinder that is under high pressure. A pressure-measuring unit and a flow meter unit are present. The oxygen is fed to a patient via an anesthetic evaporator and a mask.
DE 10 2005 012 340 B3 shows an anesthesia system with an anesthetic evaporator. In DE 10 2005 012 340 B1, a valve is located upstream of the anesthetic evaporator, so that the gas flow is sent completely or partly through the anesthetic evaporator or a bypass line during operation as intended, whereas the gas flows exclusively through the anesthetic evaporator in case of an error.
U.S. Pat. No. 4,657,710 A shows an anesthetic evaporator with an electronically controlled valve, by which a carrier gas is split into a first gas path and a second gas path, wherein the gas is enriched with a volatile anesthetic in the second gas path before it flows again into the first gas path.
DE 39 24 123 A1 and the corresponding U.S. Pat. No. 5,049,317 A show a dispensing device for gas mixtures with an anesthetic evaporator and with controllable adjusting elements, as a result of which a gas mixture flows to the patient either through a bypass line past the anesthetic evaporator and thus bridges over the anesthetic evaporator, or the gas mixture flows to and through the anesthetic evaporator to the patient by means of an evaporator line. A calibration volume with a filling level display is provided, into which opens a calibrating line, which can be separated from the evaporator line by shut-off elements. Manual or automatic calibration of the gas mixture flow meter unit is possible as a result, especially for small quantities of gas, without an interruption of the measurement of the quantity of gas being necessary.
Various dispensing systems are present at an anesthesia device for respirating and supplying the patient during and after surgery. A surgery with anesthesia of a patient can be divided into three essential time periods. There is an induction phase, a surgery phase and the phase of reversal of anesthesia or recovery phase. A quantity of gas with volatile anesthetics is typically fed to the patient by means of a mask during the induction phase, so that the patient is unconscious and free from pain. It is then possible to insert the endotracheal tube into him, with which the surgery phase proper will then start and the patient is respirated and anesthetized in the intubated state. The patient is supplied again with fresh gas via the mask during the reversal or recovery phase after removal of the endotracheal tube. The fresh gas used during the recovery phase is preferably provided with an oxygen concentration higher than the normal concentration of 21% in ambient air, so that the patient can recover his own breathing activity quite rapidly due to the increased oxygen supply. For this induction phase as well as for the reversal phase, the gas is not fed to the patient via the mixer, which mixes together the gases into a gas mixture consisting of nitrous oxide, air and oxygen during the surgery, but another, additionally present gas supply means, the so-called oxygen insufflation gas supply means is selected, by means of which oxygen can be fed to the patient as a gas at a separate port additionally and independently, besides the normal gas dispensing branch. This gas flows through the anesthetic evaporator and then reaches, enriched with anesthetic, the port for the oxygen insufflation unit and the patient via a breathing tube. The gas mixture is controlled by the mixer automatically during and under a surgery according to the settings selected by the user. The mixer is designed to mix oxygen, air and nitrous oxide with one another to form a gas mixture. The user decides during the induction how much anesthetic he adds at the anesthetic evaporator via an adjusting element. There is no active flow through the anesthetic evaporator during the recovery, so that pure oxygen is made available to the patient. This oxygen insufflation takes place in the dispensing unit via a separate control valve with a corresponding display. A so-called flow tube combined with a control valve is commonly used for this in the state of the art.
The flow tube is a floating-body flow meter, as it is described, for example, in U.S. Pat. No. 2,778,223 A. A floating body is floating in this case in a tube and moving up and down vertically at a scale and the user can dispense via the control valve and see directly how much oxygen is being dispensed from the level to which the floating body rose. The oxygen insufflation unit thus makes it possible to supply the patient with oxygen via a mask placed on the patient's face before and after the surgery. Such a device for oxygen insufflation is shown in U.S. Pat. No. 5,697,364 A1.
In addition to providing gas to the patient via the mixer and by means of the oxygen insufflation unit, there is another way to dispense oxygen to the patient. This way extends, entirely independently, besides and past any dispensing unit, directly from the oxygen admission via a switching element, the so-called O2 flush button, directly to the patient without flow through the anesthetic evaporator. Anesthetic and nitrous oxide are flushed completely out of the system by means of an oxygen blast triggered by the user by means of the O2 flush button. However, this O2 flush is not suitable for being used for oxygen insufflation, because the volume and pressure are released to the patient in an uncontrolled manner only by manually operating the button. U.S. Pat. No. 3,521,634 A shows an anesthesia device with a housing, in which a chamber is arranged for receiving a volatile anesthetic, a pressurized gas source, as well as adjustable valves and gas lines, in which anesthesia device such an O2 flush functionality is contained.
Another way of dispensing oxygen at an anesthesia system is the so-called emergency gas supply. This emergency gas supply is necessary for the anesthetist to be able, in case of failure of the mixer or in case of failure of the electric power supply, to continue the anesthesia by means of a manual oxygen dispensing unit, in practice in the form of a labeled adjusting wheel, with which a volume flow of oxygen is dispensed, and by means of the flow through the anesthetic evaporator, the so-called vapor. The anesthetist now takes over the manual respiration of the patient by means of a manual breathing bag.
An emergency oxygen gas supply unit for an anesthesia device is shown in EP 0 916 358 B1. The state of failure of the general gas supply and mixing of gases is recognized by continuously monitoring the flow through the gas-mixing valves. If the failure of a valve is recognized from a deviation from a set point, operation is immediately switched over to supplying the patient with oxygen by means of a bypass line, where manual means for dispensing the flow as well as for displaying the dispensed quantity flowing through may be additionally provided in the bypass line.
EP 0 684 049 B1 describes a manually actuated safety valve for a respirator or anesthesia device. The valve is designed to allow two different volume flows to flow through the valve from an inlet duct to an outlet duct at two different working points in addition to the closed state.
U.S. Pat. No. 6,250,302 B1 shows a process and a device in conjunction with a respirator, wherein the gas is supplied via a gas mixer for a plurality of possible applications for respirating a patient. A gas mixture is fed to the patient via a movable piston, with a quantity of fresh gas flowing into the piston via a gas mixer.
Thus, the types of dispensing oxygen and gases to the patient with an anesthesia device are described in the state of the art.
These four ways are present essentially independently from each other. Gas dispensing for the operation during the surgery via the gas mixer for mixing oxygen, nitrous oxide and air with subsequent flow through the anesthetic evaporator is the essential controlled way of carrying out the anesthesia. The emergency gas supply is designed for the case of failure of the mixer or of the electric power supply to enable the anesthetist to continue the anesthesia even without the mixer or additional electric systems in the anesthesia device functioning. The oxygen insufflation unit, which is used especially during induction and reversal, is designed to bring oxygen directly to the patient via an additional branch, dispensed via a flow tube, to an additional port with flow through the anesthetic evaporator and hence an enrichment of the oxygen with anesthetic gas, usually by means of a mask or a nasal prong. The O2 flush is a system arranged in parallel thereto, which can introduce an oxygen blast into the system by means of a button without flow through the anesthetic evaporator to flush anesthetic gases out of the respiration system.
Due to these four ways of dispensing being separately present in the system, the design effort for providing oxygen dispensing in three different ways and for also making available an oxygen blast as a possibility of dispensing in an additional, fourth way, is not insignificant.